A wearable device developed at Stanford University can detect stress levels by measuring the amount of cortisol in the user's sweat.
Cortisol is a hormone that stays on all day long and off, often in terms of stress. According to the Stanford team, existing methods of measuring the hormone can take several days. This delay makes it difficult to accurately inform medical treatments, although cortisol levels can be an indicator of adrenal and pituitary function.
The portable prototype, made in the laboratory of materials scientist Alberto Salleo, is a patch that dissipates sweat from the skin. Postdoc Onur Parlak built a stretchy, rectangular sensor around a membrane that binds specifically to cortisol only. Attached to the skin, it sucks passively through holes in the bottom of the patch. The sweat collects in a reservoir covered by the cortisol-sensitive membrane. Charged ions such as sodium or potassium, which also occur in sweat, pass through the membrane unless they are blocked by cortisol. It is these charged ions that the sensor detects because cortisol itself has no charge and presents a unique challenge.
"We are particularly interested in welding sensor technology because it provides non-invasive and continuous monitoring of various biomarkers for a range of physiological conditions," said Parlak, lead author of the study, which was published in Science . "This provides a novel approach to the early detection of various diseases and the evaluation of sports performance."
Parlak showed for the first time that the device was measured in the laboratory until the gold standard clinical test. He then tested it in the real world when he and two volunteers ran for 20 minutes with the patches on their arms. Both in the laboratory and in the real world, the results were similar to the gold standard. Reads are done by connecting the patch to an external device, but there are plans for a fully integrated version of the patch to be developed. There is hope that the patch could be used to detect stress levels in children who are unable to communicate and in nonverbal patients.
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